In the manufacture of glass fiber reinforced polymeric composites, many of the properties of the composites are directly attributable to the properties of the glass fiber reinforcement. Accordingly, anything that deleteriously affects the desired physical properties of the glass fibers, such as abrasion of the fibers during their processing, is desirably avoided. Moreover, the degree to which the composite benefits from the inclusion of the glass fibers is largely dependent on the chemical coupling that occurs at the fiber polymer interface. For these reasons, glass fibers intended to be used as reinforcing elements in articles fabricated from polymeric or resinous materials are usually provided with a light-weight size coating to protect the fibers from damage by abrasion during processing and fabrication, and/or to enhance the reinforcing interaction between the fibers and the matrix material. Such size coatings typically comprise a film-forming polymeric or resinous component, a lubricant to reduce interfilament abrasion, and a glass-resin coupling agent, such as a partially hydrolizable organosilane or hydrozylate thereof.
Such size coatings are usually deposited on the glass fibers during their production, which is ordinarily by attenuation of a plurality of streams of molten glass issuing from a reservoir through a corresponding plurality of orifices in a bushing, and solidification of the attenuated filaments by cooling. The coating is typically applied to the fibers as a liquid solution or dispersion in a volatile medium, from which the ultimate size coating is deposited on the fibers by evaporation of the medium and any other volatile components. Evaporation of the liquid medium may occur either before or after the fibers have been collected into a package, as by winding onto a suitable collet, or chopped into discrete lengths.
While a number of organosilanes, or hydrozylates thereof, either alone or in various mixtures, have been employed as coupling agents in such sizing compositions, the advantages provided by the particular mixture of organosilanes in the sizing composition of the present invention have not heretofore been appreciated in the art.